Reactive gas shaped charge and method of use

ABSTRACT

A perforating system including a perforating gun having a perforating gun body housing shaped charges oriented outwardly from the gun body and connected to a detonation system for deployment into a wellbore. The shaped charges include at least a case, a liner and explosive material that is thermally stable and of a composition that allows for reaction with metals, debris or formation walls in order to improve fluid flow from the formation upon perforating. Shaped charge can also employ differences in composition moving from the apex to the skirt of the liner in order to achieve different perforating characteristics upon detonation of the explosive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of and priority to U.S. Provisional Application No. 62/396,614, entitled “Reactive Gas Shaped Charge And Method Of Use”, filed on Sep. 19, 2016, the entire disclosure of which is hereby incorporated herein by reference.

BACKGROUND

After drilling and casing of an oil or gas well, the well is opened to the surrounding formation for the ingress of oil or gas. The well is opened by perforating the casing and the rock formation beyond the casing using shaped charges. A shaped charge generally comprises an explosive material located between a case and a liner. A portion of the liner forms a jet which is propelled away from the case when the shaped charge is detonated. The jet is propelled through the casing and into the formation to form a perforation which facilitates the ingress of oil and/or gas.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the described implementations can be more readily understood by reference to the following description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic illustration of an example of a perforation system having a plurality of shaped charges deployed in a wellbore, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of an example of a shaped charge, according to an embodiment of the disclosure;

FIG. 3 illustrates a method for perforating a well in accordance with various embodiments of the present invention.

DETAILED DESCRIPTION

The following description includes the best mode presently contemplated for practicing the described implementations. This description is not to be taken in a limiting sense, but rather is made merely for the purpose of describing the general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims.

A downhole perforating gun can include an explosive that can be discharged to generate one or more openings in a downhole structure and, for example, a surrounding geologic environment. As an example, such one or more openings may be utilized for fluid flow. For example, liquid and/or gas in a reservoir may flow via such one or more openings. As an example, hydrocarbons from a reservoir may flow into the wellbore via the openings and/or fluid may be injected into a geologic environment via the one or more openings. However, during the process of explosive perforation, metal and formation debris can be deposited in the formed tunnels which can reduce fluid flow to and from the geologic environment. Many components that may be found obstructing perforation tunnels post perforation are not readily oxidizeable materials and therefore difficult to remove by post facto chemical reaction.

An explosive can include chemical explosive material having a high reaction rate that creates high combustion pressures. As an example, an explosive may be categorized as being a primary-high explosive or as a secondary-high explosive. A primary-high explosive can be sensitive, can be detonated easily and can be used in percussion and electrical detonators. A secondary-high explosive can be less sensitive, utilize a high-energy shock wave to achieve detonation and can be safer to handle. As an example, a secondary-high explosive can be used in elements of a ballistic chain (e.g., other than the detonator), such as in a detonating cord and/or one or more shaped charges. An explosive may also generate gas that can chemically react with a target and may potentially remove debris from a perforation tunnel such that well production can be improved.

Referring generally to FIG. 1, an example of a perforating system 20 is illustrated as deployed in a wellbore 22 via a conveyance 24. In this example, the wellbore 22 extends into a subterranean formation 26 from a surface location 28 and is lined with a casing 30. The perforating system 20 comprises a perforating gun 32 having a perforating gun body 34. The perforating gun body 34 may have a variety of structures and may be constructed with many types of components. A plurality of shaped charges 36 is mounted to the perforating gun body 34, and each of the shaped charges 36 is oriented outwardly from the gun body 34.

As an example, a perforating gun 32 can be a capsule gun or capsule-charge gun. A capsule can be an individual shaped charge 36 sealed in a pressure-tight protective capsule and a series of capsules may be mounted on a carrier strip or links. A perforating gun 32 can be a hollow carrier gun which can be a pressure-tight metal tube in which shaped charges 36 are positioned.

As an example, a perforating gun 32 can be operatively coupled to a wireline cable head, a tubing-conveyance assembly, etc. A perforating gun 32 can include mating features such as, for example, threads, bayonets, etc. One or more centralizers may be installed on a perforating gun assembly in order to prevent the gun from coming into contact with the tubing during placement and detonation of the shaped charges.

The shaped charges 36 may be connected to a detonation system 38 having a detonation control 40 which provides signals to a detonator or detonators 42 to initiate detonation of shaped charges 36. In many applications, the detonation system 38 may utilize a detonator 42 in the form of detonation cord properly positioned to initiate detonation of the shaped charges 36. When detonator 42 comprises detonation cord, the detonation cord is routed to the shaped charges 36 and portions of the detonation cord are placed into cooperation with explosive material located in the shaped charges 36. In some applications, the shaped charges 36 are placed in a staggered pattern along the perforating gun body 34 and linked by the detonator/detonation cord 42 which is routed back and forth between the staggered shaped charges 36. The detonation cord enables a desired, controlled detonation of the plurality of shaped charges. Upon detonation, the shaped charges 36 explode and create a jet of material which is propelled outwardly to create perforations 44 which extend through casing 30 and into the surrounding subterranean formation 26. The number and arrangement of shaped charges 36 can vary depending on the parameters of a given perforation application. Additionally, the shaped charges 36 may be detonated in separate groups, at staggered intervals or a plurality of perforating guns 32 may be employed to perforate different zones of subterranean formation 26.

Referring generally to FIG. 2, an example of one of the shaped charges 36 is illustrated. In this embodiment, shaped charge 36 comprises a case 46, a liner 48, and an explosive material 50 positioned between the case 46 and the liner 48. The liner 48 extends generally between a first portion or apex 52 and a second portion or skirt 54. By way of example, the liner 48 may be cup-shaped with the apex 52 forming the bottom of the cup and the skirt 54 forming the rim of the cup. The liner 48 may be formed with a powder material 56 having characteristics which change between the apex 52 and the skirt 54. In some applications, however, non-powdered material also may be combined into the liner 48 to help provide the changing characteristic or characteristics.

The liner 48 may be constructed such that the powder material 56 has differences in compositional parameters, e.g. powder density or other material properties, moving from the apex 52 to the skirt 54. The differences in material properties may be selected to optimize or otherwise adjust the jet velocity and jet mass of the liner 48 upon detonation of explosive material 50. The changes in compositional parameters may be achieved by utilizing a variety of powder material blends, e.g. mixtures, between the apex 52 and the skirt 54. In some applications, the powder material 56 may have a changing proportion of materials along the axis of the liner 48 (i.e. varied between the apex 52 and the skirt 54) to achieve a desired continuity of liner properties, e.g. continuity of density or mass, with a corresponding, desired jet velocity and jet mass. The changing characteristic, e.g. changing material properties, along the liner 48 may be achieved by a variety of powder material techniques. However, the liner 48 also may be constructed via three-dimensional (3-D) printing techniques which enable variation of material properties, e.g. variation of material compositional parameters, at different regions throughout the liner 48. For example, 3-D printing techniques may be used to control and vary the porosity along liner 48 to obtain desired jet properties.

By way of example, the powder material 56 used to form liner 48 may be a powder metal material. The powder metal material may be formed from various mixtures of metal powders (or metal and non-metal powders) depending on the perforating characteristics desired for a given application. Examples of metal powders include tungsten (W) powder, copper (Cu) powder, lead (Pb) powder, titanium (Ti) powder, and other metal powders. The various metal powders may be mixed in many different types of compositions and those compositions may be varied between the apex 52 and the skirt 54 of liner 48. The composition of the powder metal material 56 and the differences in composition moving from the apex 52 to the skirt 54 is selected to achieve different perforating characteristics upon detonation of the explosive material 50. Additionally, the powder material 56 may incorporate a binding material formed as a coating or other type of layer on the powder materials used to form the liner 48.

In a perforating operation, the selection of a shaped charge explosive 50 may be based at least in part on time-temperature specifications associated with at least a portion of the operation. For example, where time-temperature specifications indicate that a charge is to be exposed to a time-temperature profile that would allow for possible degradation of explosive, then one or more categories of explosives may be excluded and/or one or more particular categories of explosives may be included in a group from which a selection can be made.

In the foregoing example, as to selection of an explosive, the criteria involve at least temperature which dictate use of a material that is thermally stable. It is also desirable that the material be capable of improving flow by chemical means (via reaction with metallic or other debris and/or reaction with the formation walls). As an example, an energetic intermediate comprising 4,4′-dichloro-2,2′, 3,3′, 5,5′, 6,6′-octanitroazobenzene (DCONAB), or its congeners, maybe incorporated into a shaped charge explosive, either exclusively or in combination with other explosive materials.

A shaped charge as discussed above incorporating DCONAB, or any of its congeners, can be initiated to produce a jet that creates a perforation tunnel through a casing and into a geological formation whereupon the explosion creates a byproduct gas that reacts with metal and debris within the perforation tunnel so as to clear the tunnel of these undesirable components.

In the examples of FIGS. 1 and 2, an explosive or energetic material can be exposed to a temperature in excess of 100 degrees C. For example, a downhole environment may be at a temperature above about 250 degrees F. (e.g., above about 121 degrees C.). In such environments, an explosive or energetic material may degrade (e.g., decompose). As an example, an environment may be a harsh environment, for example, an environment that may be classified as being a high-pressure and high-temperature environment (HPHT). A so-called HPHT environment may include pressures up to about 138 MPa (e.g., about 20,000 psi) and temperatures up to about 205 degrees C. (e.g., about 400 degrees F. and about 480 K), a so-called ultra-HPHT environment may include pressures up to about 241 MPa (e.g., about 35,000 psi) and temperatures up to about 260 degrees C. (e.g., about 500 degrees F. and about 530 K) and a so-called HPHT-hc environment may include pressures greater than about 241 MPa (e.g., about 35,000 psi) and temperatures greater than about 260 degrees C. (e.g., about 500 degrees F. and about 530 K). As an example, an environment may be classified based in one of the aforementioned classes based on pressure or temperature alone.

The variation in the structure of the shaped charge liner and/or in the composition of the shaped charge liner can be used to facilitate perforating in many well related applications. The shaped charges described herein may be used in wells drilled from the Earth's surface and in subsea wells. However, the shaped charges and the shaped charge liners also may be used in non-well applications in which perforations are formed through and/or into a variety of materials. The variable characteristics of the liner may be used to achieve the desired jet for optimized perforation performance in many types of applications.

With reference to FIG. 3, methods for perforating in a well include: (1) disposing a perforating gun in the well, wherein the perforating gun comprises a shaped charge having a charge case, an explosive disposed inside the charge case, and a liner for retaining the explosive in the charge case; (2) detonating the shaped charge to form a perforation tunnel in a formation zone whereby byproduct gas resulting from the explosion reacts with metal, debris and/or the formation to improve flow; (3) optionally performing one of the following: (i) pumping an acid downhole, (ii) pumping a fracturing fluid downhole, (iii) pumping an injection fluid downhole, or (iv) circulating a completion or wellbore fluid downhole to further clear residue and debris from the perforation tunnel. After such operation, a treatment fluid may be injected into the formation and/or the formation may be produced. In alternative embodiments, a fluid may be injected in the formation (e.g., produced water) for storage.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A shaped charge comprising: a case; a liner; and an explosive material positioned between the case and the liner.
 2. The shaped charge of claim 1 wherein the explosive material is thermally stable above 100 degrees F.
 3. The shaped charge of claim 1 wherein the explosive material comprises 4,4′-dichloro-2,2′, 3,3′, 5,5′, 6,6′-octanitroazobenzene (DCONAB).
 4. The shaped charge of claim 1 wherein the explosive material comprises a congener of 4,4′-dichloro-2,2′, 3,3′, 5,5′, 6,6′-octanitroazobenzene (DCONAB).
 5. The shaped charge of claim 2 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 6. The shaped charge of claim 3 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 7. The shaped charge of claim 4 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 8. The shaped charge of claim 1 wherein the liner comprises a powder metal material of one or more of tungsten (W) powder, copper (Cu) powder, lead (Pb) powder, or titanium (Ti) powder.
 9. A method comprising: disposing a perforating gun in the well, wherein the perforating gun comprises a shaped charge having a charge case, an explosive disposed inside the charge case, and a liner for retaining the explosive in the charge case; and detonating the shaped charge to form a perforation tunnel in a formation zone whereby byproduct gas resulting from the explosion reacts with metal, debris and/or the formation to improve flow.
 10. The method of claim 9 wherein the explosive comprises 4,4′-dichloro-2,2′, 3,3′, 5,5′, 6,6′-octanitroazobenzene (DCONAB).
 11. The shaped charge of claim 9 wherein the explosive material comprises a congener of 4,4′-dichloro-2,2′, 3,3′, 5,5′, 6,6′-octanitroazobenzene (DCONAB).
 12. The shaped charge of claim 10 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 13. The shaped charge of claim 11 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 14. The shaped charge of claim 9 wherein the liner comprises a powder metal material differing in composition from an apex to a skirt of the liner.
 15. The shaped charge of claim 9 wherein the liner comprises a powder metal material of one or more of tungsten (W) powder, copper (Cu) powder, lead (Pb) powder, or titanium (Ti) powder.
 16. The shaped charge of claim 10 wherein the liner comprises a powder metal material of one or more of tungsten (W) powder, copper (Cu) powder, lead (Pb) powder, or titanium (Ti) powder.
 17. The shaped charge of claim 11 wherein the liner comprises a powder metal material of one or more of tungsten (W) powder, copper (Cu) powder, lead (Pb) powder, or titanium (Ti) powder.
 18. The method of claim 9 further comprising performing at least one of the following: (i) pumping an acid downhole, (ii) pumping a fracturing fluid downhole, (iii) pumping an injection fluid downhole, and (iv) circulating a completion or wellbore fluid downhole to clear residue and debris from the perforation tunnel. 